In recent years, systems for television conference or the like are becoming widespread which transmit/receive a plurality of real-time streams such as video, sound among terminal apparatuses via a best-effort network such as the Internet.
In a best-effort network, available bands change as an environment changes, and it is therefore necessary to dynamically change the amount of code of each real-time stream. PTL 1 discloses a scheme in which a large code amount is assigned to more complicated real-time streams.
In the best-effort network, when an environment deteriorates, packet losses occur. For this reason, the best-effort network employs a scheme in which lost packets are recovered using a redundancy code packet generated by FEC (Forward Error Correction) or retransmission of packets. When FEC is used, the greater code amount is assigned, the more redundancy code packets can be generated, and it is thereby possible to increase recovery strength of packets.